LDL is oxidized to oxidized LDL (OxLDL) that is rapidly taken up by macropnages leading to coronary artery disease (CAD). Paraoxonase (PON), a HDL-bound polymorphic enzyme, lowers OxLDL level and thus prevents CAD.PI hypothesizes that light drinking (13-40 g/day) increases serum PON level and thereby lowers OxLDL by preventing its formation or by destroying it and thus has a cardioprotective effect, whereas heav^ drinking (>80g/day) has the opposite effects. PI has the following new data to support his hypothesis:! Serunr PON activity is increased 3.95-fold (p<0.001) in light drinkers, but decreased by 45% (p<0.001) in drinkers compared to nondrinkers. 2. HDL-PON inhibited LDL oxidation that is preventedby prior incubatior of HDL with either anti-PON or EDTA. 3. HDL-PON also destroyed OxLDL and inhibited OxLDL uptake b) macrophages. 4. Hepatic PON mRNA relative to GAPDH mRNA is increased by 59% (p < 0.001) in ligh alcohol-fed and decreased by 51% (p < 0.001) in heavy alcohol-fed rats compared to controls. Therefore, P proposes to delineate the action of alcohol in causing diametrically opposite effects on PON and OxLDL status, Studies in humans: PI will determine serum PON activity and protein in light, heavy and non-drinker; without liver disease before and after 4- & 8-week abstinence and correlate with plasma oxidizedLDL status and incidence of CAD by qualified cardiologists. PI will test serum samples from each study group fo their ability to (i) inhibit LDL oxidation (ii) destroy OxLDL and (iii). prevent OxLDL uptake by macrophages. P will also genotype PON genes in the study groups to correlate their susceptibility to light and heavy alcoho drinking. Finally, PI will test whether light or heavy drinking up-regulated or down-regulates PONS allozyme. Studies in rats: Since PON is expressed only in the liver (except PONS), molecular regulation of P0r> by alcohol can only be studied in an animal system like rat under well-defined conditions. PI will determinethe effects of ethanol dosage and duration of exposure on hepatic PON concentration and its mRNA level b} Western Blot and Northern Blot analyses, respectively. PI will then determine whether ethanol regulates PON mRNA at transcriptional or post-transcriptional level by Nuclear-run-on and mRNA stability assays. These investigations are likely to lead to new insights in our understanding of the cardioprotective effects of ligh drinking and proatherogenic effects of heavy drinking both at clinical and at molecular levels.